[Tutor] list.index() question

[Robert Berman]

On 12/08/2011 05:03 PM, Steven D'Aprano wrote:
> Robert Berman wrote:
>> Hi,
>>
>> Assuming a list similar to this: l1=[['a',1],['b',2],['c',3]] and I 
>> want to get the index of 'c'.
>
> You will need to explain what you mean by "the index of 'c'".
>
> Do you mean 0, because 'c' is in position 0 of the sub-list ['c', 3]?
>
> Or do you mean 2, because 'c' is in the sub-list at position 2?
>
> What happens if there is a sub-list ['d', 'c']? Should that also 
> count? What about sub-sub-lists, should they be checked too?
>
> Here is a version which checks each sub-list in turn, and returns the 
> index of any 'c' it finds of the first such sub-list.
>
> def inner_find(list_of_lists):
>     for sublist in list_of_lists:
>         try:
>             return sublist.index('c')
>         except ValueError:
>             pass  # go to the next one
>     # If not found at all:
>     raise ValueError('not found')
>
>
> Here's a version which finds the index of the first sub-list that 
> begins with 'c' as the zeroth element:
>
> def match_sublist(list_of_lists):
>     for i, sublist in enumerate(list_of_lists):
>         if sublist and sublist[0] == 'c':
>             return i
>     raise ValueError('not found')
>
>
>
>
> Other variations on these two techniques are left for you to 
> experiment with.
>
>
>
Thank you Steven and Joel. You have given me information to experiment 
with which is most appreciated.

Robert
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